SP5 Light and the Electromagnetic Spectrum Flashcards
What is a normal?
A line drawn at right angles to the barrier or mirror in a ray diagram
What is a ray diagram?
A way of modelling what happens when light is reflected or refracted
Where are the angle of incidence and the angle of refraction measured from?
The normal
State the law of reflection
When waves are reflected, the angle of reflection is equal to the angle of incidence
What happens to light when it travels through different materials?
It changes speed and direction
Define refraction
The change in the direction of a wave at a boundary
When is there no change in direction when a light ray hits the boundary?
If it hits the boundary at right angles
What is the medium light travels the fastest in?
Air
What is the medium light travels the slowest in?
Solids (glass)
What happens when light enters into a medium wherein it travels slower than the previous one?
It bends towards the normal
What happens when light enters into a medium wherein it travels faster than the previous one?
It bends away from the normal
What is total internal reflection?
Sometimes, when light is moving into a less dense material as compared to one it was already in, instead of being refracted, it is reflected inwards
When does total internal reflection occur?
The angle of incidence is greater than the critical angle and the incident material is denser than the second material
What are the two conditions for total internal reflection?
- angle of incidence > critical angle
- the incident material is denser than the second material
What is the critical angle?
The angle of incidence wherein the angle of refraction is 90 degrees
Why can luminous objects be seen?
They give off light
What is specular reflection?
Reflection from a smooth, flat surface
What is total internal reflection used in?
- prisms
- optical fibres
Describe a typical image produced from a specular reflection
- upright
- virtual
Define diffuse reflection
Instead of forming an image, the reflected light is scattered in all directions
What kind of image does a diffuse reflection cause?
- distorted
- no image at all
State the colours in order of increasing frequency and decreasing wavelength
- red
- orange
- yellow
- green
- blue
- indigo
- violet
When is light absorbed?
When white light shines on an opaque object
Give an example of the transmission of a wave at a boundary
Transparent objects, such as glass transmit waves because they barely absorb any light
What are filters?
Pieces of transparent materials that absorb some of the colours in white light and transmit a specific colour
When does an object appear black?
When it absorbs all wavelengths of visible light
What is a lens?
A shaped piece of transparent glass or plastic that refracts light